1. Technical Field of the Invention
The present invention relates to a coefficient measurement apparatus, an effect impartment apparatus, and a musical sound generating apparatus using the effect impartment apparatus which can fully and reliably reproduce resonance of an acoustic musical instrument.
2. Description of the Related Art
When a musical sound of an acoustic musical instrument is amplified for the sake of live play or the like, the sound of the musical instrument is generally collected by a microphone. However, when the musical sound of the acoustic musical instrument is received by the microphone, there is a problem in that howling easily occurs. Accordingly, in many cases, a piezoelectric pickup is used to pick up string vibrations and to output them as an audio signal.
However, using the piezoelectric pickup, it is not possible to sufficiently pick up a resonant sound of an acoustic musical instrument (for example, a body resonance of an acoustic guitar). Thus, it has been suggested that acoustic effects such as delay or reverb be imparted to reproduce the resonance sound (for example, see Patent Reference 1). It has also been suggested that an FIR filter be used to perform signal processing to reproduce an echo feeling (for example, see Patent Reference 2).
[Patent Reference 1] Japanese Patent Application Publication No. 2003-15644
[Patent Reference 2] Japanese Patent Application Publication No. 2005-24997
However, simply imparting acoustic effects such as delay or reverb as in Patent Reference 1 cannot reproduce a resonance feeling such as a box resonance of an acoustic musical instrument (specifically, emphasis or attenuation of a specific frequency).
When the FIR filter is used as in Patent Reference 2, there is a need to previously measure an impulse response. To measure an impulse response, an impulse hammer or vibrator is generally used to apply a vibration. However, measurement using the impulse hammer has a problem in that measurement variation is high, failing to achieve reliable measurement. Measurement using the vibrator also has a problem in that the measured resonance characteristics are different from those of actual play since the vibrator is brought into contact with the musical instrument.